1. Field of the Invention
The present invention relates generally to microphones. More particularly, this invention relates to a microelectromechanical (MEMS) microphone.
2. Description of Related Art
There have been a number of disclosures related to building microphone elements on the surface of a silicon die. Certain of these disclosures have come in connection with the portable device field for the purpose of reducing the size of the device. While these disclosures have reduced the size of the device, they have not disclosed how to protect the transducer from outside interferences. For instance, transducers of this type are fragile and susceptible to physical damage. Furthermore, they must be protected from light and electromagnetic interferences. For these reasons, the silicon die must be shielded.
Typically, such a MEMS microphone generally includes a MEMS die having a silicon substrate, a backplate arranged on the substrate, and a moveable diaphragm separated from the backplate for forming a capacitor. While external sound waves reach the diaphragm, the diaphragm will be activated to vibrate relative to the backplate, which changes the distance between the diaphragm and the backplate and changes the capacitance value. As a result, the sound waves are converted into electrical signals.
Such typical microphones are disclosed in U.S. Pat. No. 7,166,910 B2, U.S. Pat. No. 7,242,089 B2, and U.S. Pat. No. 7,023,066 B2. However, the shields in these patents are thin conductive layers electroplated on non-conductive layers, which increases production cost. Further, the thin conductive layers would peel off the non-conductive layers. As a result, an MEMS microphone having an improved shield is desired.